
def fibonacci(m, n):
    pre = 0
    cur = 1

    for _ in range(m, n):
        temp = cur
        cur = (pre + cur)
        pre = temp

    return cur


if __name__ == "__main__":
    m, n = map(int, input().split())

    if m > n:
        print(0)
    else:
        result = fibonacci(m, n)
        print(result)
